title: A comparison of surface roughness and composite/enamel bond strength of human enamel following the application of the Nd:YAG laser and etching with phosphoric acid.
abstract: OBJECTIVE
  This study was conducted to evaluate enamel morphology after laser etching and acid etching and to determine the shear bond strength of composite to acid-etched and laser-treated enamel.
  
  
  METHODS
  Enamel from freshly extracted permanent molar teeth was subjected to either laser treatment with an Nd:YAG laser in different laser parameters or was exposed to 37% phosphoric acid for 60 s (Gluma Gel, Bayer Dental). Surface profile analysis of the enamel was undertaken with a Perthometer (S8P, Feinpruif). The results were analyzed by SPSS/PC multiple range test and Student-Newman Keuls procedure. Specimens were examined in a scanning electron microscope (SEM). Shear bond strengths of acid-etched and laser-etched enamel/composite (Brilliant Dentin, Coltene AG and Pekalux, Bayer Dental) were also determined. These results were compared by SPSS/PC multiple range test.
  
  
  RESULTS
  The acid-etched specimens exhibited a qualitatively different type of enamel surface morphology when compared with the laser-treated specimens. Laser treatment at higher exposures resulted in the formation of microcracks and fissures. No significant difference in surface roughness was observed between laser-treated enamel in three different parameters (10 pps, 0.8 W; 15 pps, 1.0 W; 20 pps, 1.25 W) and acid-etched specimens. However, the mean bond strengths of all laser-treated specimens, regardless of the test parameters, were significantly lower (p < 0.05) than the acid-etched enamel specimens.
  
  
  CONCLUSIONS
  Although the laser roughened the surface of the enamel, it did not provide a surface as retentive as a surface treated with conventional acid etching. It is concluded from this study that the Nd:YAG laser operated under the conditions described cannot be recommended as a viable alternative to acid etching.
authors.affiliation: Department of Dental Medicine and Surgery, University Dental Hospital, Manchester, United Kingdom.
authors.forename: M T
authors.initials: MT
authors.lastname: Ariyaratnam
authors.forename: M A
authors.initials: MA
authors.lastname: Wilson
authors.forename: I C
authors.initials: IC
authors.lastname: Mackie
authors.forename: A S
authors.initials: AS
authors.lastname: Blinkhorn
mesh_terms: D000134:Acid Etching, Dental; D003188:Composite Resins; D001840:Dental Bonding / Q000379:methods*; D003743:Dental Enamel / Q000187:drug effects* / Q000528:radiation effects* / Q000648:ultrastructure; D005069:Evaluation Studies as Topic; D006801:Humans; D007834:Lasers / Q000009:adverse effects*; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D009354:Neodymium; D010756:Phosphoric Acids / Q000494:pharmacology; D019279:Resin Cements; D013499:Surface Properties / Q000187:drug effects / Q000528:radiation effects; D013718:Tensile Strength
chemical_list: D003188:Composite Resins; D010756:Phosphoric Acids; D019279:Resin Cements; C069353:Brilliant Dentin resin; C076985:Pekalux; D009354:Neodymium; C030242:phosphoric acid